People who put on weight are more likely to develop knee pain than those who stay the same or lose weight, says a new study. People who shed pounds saw only a modest improvement in knee pain, however, researchers from Monash University in Melbourne, Australia, found. "Preventing weight gain, almost no matter what weight you start out at, is going to be the key to preventing knee problems," said Dr. Susan Bartlett, who has studied joint pain and obesity at McGill University in Montreal, Canada, and was not involved in the study.